Recent publications in Nature Genetics, August, 1999 (Young et al, page 316; Bodzioch et al, page 347; Brooks-Wilson et al, page 335, and Rust et al, page 352) showed that humans with mutations in the gene ABCA1 (also previously known in the art as ABC1) have low levels of high density lipoprotein (HDL). Low HDL levels are a risk factor for atherosclerosis, myocardial infarction and related conditions such as ischemic stroke. Therefore, increasing the expression of the ABCA1 gene would be expected to increase HDL levels and decrease the occurrence of atherosclerosis, myocardial infarction and related conditions such as ischemic stroke. It has been reported that expression of the ABCA1 gene is increased by cholesterol loading of cells (Langmann et al, Biochem. Biophys. Res. Comm., 257, 29-33 (1999)). LXRα is a nuclear receptor that is required for the induction of cholesterol 7α-hydroxylase in mouse liver following cholesterol feeding (Peet et al, Cell, 93, 693-704 (1998)). LXRα and LXRβ are activated by 22-(R)-hydroxycholesterol and other oxysterols (Janowski et al. Proc. Natl. Acad. Sci USA, 96, 266-271 (1999), Thomas A. Spencer et al. J. Med. Chem., 44, 886-897, (2001)). Some non-steroidal small molecule agonists of LXRα and LXRβ have been reported to affect circulating HDL levels, cholesterol absorption, reverse cholesterol transport and ABCA1 expression in vivo (J. R. Schultz, et al. Genes & Devel. 14, 2831-2838, (2000), J. J. Repa et al. Science, 289, 1524-1529, (2000)) It has been found that LXRα and/or LXRβ cause the induction or regulation of ABCA1 expression, and that small molecule ligands of LXR are useful as drugs to increase the expression of ABCA1, increase levels of HDL and thereby decrease the risk of atherosclerosis, myocardial infarction and related conditions such as peripheral vascular disease and ischemic stroke.
The various dyslipidemic conditions, which are risk factors for atherosclerosis, are currently treated with several different classes of drugs, such as statins which are HMG-CoA reductase inhibitors, bile acid sequestrants (e.g., cholestyramine and colestipol), nicotinic acid (niacin), and fibrates. However, except for niacin, most of these treatments do not raise HDL as their primary effect. With favorable outcomes in many human studies, the statin class of drugs is used to modulate LDL and, to a lesser extent, HDL and triglycerides. Conditions principally characterized by elevated plasma triglycerides and low HDL are frequently treated with drugs belonging to the fibrate class. The fibrates are PPAR alpha agonists that lower triglycerides and raise HDL in many instances. There are no currently marketed drugs whose principal actions are mediated by LXR.
We have now discovered a new class of small molecules which are LXR ligands, i.e., LXRα and/or LXRβ ligands, and are therefore expected to be useful for modulation of ADL levels, ABCA1 gene expression and reverse cholesterol transport. The instant compounds have been shown to raise plasma levels of HDL in animal models and to increase cholesterol efflux from cells in vitro. These biological activities are critical for reverse cholesterol transport.
The novel compounds of this invention are intended as a treatment for dyslipidemias, especially low plasma HDL cholesterol levels, as well as for treatment and/or prevention of lipid accumulation in atherosclerotic plaques, which is an underlying cause or aggravating factor in atherosclerosis.